The invention relates to processes and apparatus for removing coatings, and particularly to a process and apparatus for removing at least part of a coating from a predetermined portion of a photoreceptor.
In electrophotography, and particularly in xerographic copying machines, coated substrates such as photoreceptor belts or cylindrical photoreceptor drums are common. Photoreceptor embodiments include at least one coating of photosensitive material, which can be formed on the photoreceptor by known techniques such as immersion or dip coating.
The peripheral ends of a coated photoreceptor are used to engage with flanges in a copier's drive mechanism and/or to support a developer housing. Also, the ends are often treated to be electrically conductive. Thus, both the outer and inner peripheral ends of a photoreceptor must be free of coating material.
Conventionally, the ends of a photoreceptor are masked before coating to prevent them from being coated. In dip coating, the upper end of the photoreceptor drum might be kept free of coating material by orienting the drum vertically and dipping the drum into a bath of coating material to a predetermined depth. However, the coating formed over the lower end of the photoreceptor must still be removed, usually by mechanically wiping the lower end and/or by applying solvents to it. Chemical treatments can cause solvent droplets or vapor to contact the coating in regions that are not intended to be removed, reducing the quality of the resulting photoreceptor. Furthermore, organic solvents have a limited useful life and can be hazardous to work with. Mechanical techniques for removing coatings are cumbersome, inefficient, and often produce photoreceptors of unacceptable quality.
Japanese Publication No. 3-144,458 discloses a process that attempts to remove coatings from the ends of a photoreceptor without mechanical or chemical treatment. A laser beam from an yttrium-aluminum-garnet laser is irradiated at the end portions of a photoreceptor drum to burn or sublimate the photoreceptor coating. Japanese Publication No. 3-194,131 discloses a similar process in which laser energy is directed at the ends of a photoreceptor in an effort to completely remove the coating.
Although these laser treatment processes are intended to completely remove coatings, it has been found that many materials commonly used in photoreceptor coatings are melted, rather than vaporized, by these processes. The molten coating subsequently hardens and must be removed by chemical or mechanical means. Moreover, burning the coating with a high-intensity laser can damage the photoreceptor substrate. These processes therefore yield less than satisfactory results in many instances.